Glycated hemoglobin as one of hemoglobin derivatives is an item that is often measured for early detection of lifestyle diseases, because the glycated hemoglobin enables determination of a blood sugar level in normal condition, excluding an influence of variation in blood sugar due to a meal. The glycated hemoglobin is also referred to as hemoglobin Alc, and it is hemoglobin included in blood erythrocytes, to which glucose is bonded. The glycated hemoglobin is quantified as an abundance ratio of glycated hemoglobin to hemoglobin.
As a glycated hemoglobin measurement method, there is a method utilizing immune reaction. The measurement method utilizing immune reaction is performed as follows. Initially, a blood sample is hemolyzed to extract hemoglobin out of blood erythrocytes. Next, in order to determine whether the hemoglobin is non-glycated hemoglobin or glycated hemoglobin, the cubic structure of the hemoglobin is changed to expose a glycated portion of hemoglobin protein from the cubic structure to the outside (denaturalization of hemoglobin), and further, the glycated portion is reacted with an antibody that specifically recognizes the glycated portion, thereby to immunologically measure the amount of the glycated hemoglobin.
As an example of a hemoglobin denaturalization method, there is a method of denaturalizing hemoglobin with negative ions in a lithium salt form (refer to Patent Document 1). To be specific, in an analysis method for measuring a specific hemoglobin derivative in a blood sample, (a) the blood sample is processed with a dissolution/denaturalization reagent, thereby dissolving blood erythrocytes, and denaturalizing a detectable amount of the derivative which is released from the blood erythrocytes, and (b) a resultant mixed solution is tested by immunoassay with respect to the amount of the denaturalized hemoglobin derivative that exists in the mixture solution. This method uses, as the dissolution/denaturalization reagent, negative ions in a lithium salt form which can dissolve the blood erythrocytes and denaturalize the hemoglobin derivative, and thereby the dissolution and the denaturalization of the hemoglobin derivative can be achieved speedily with the lithium salt concentration that does not significantly interfere with the immunoassay process.
Further, as another denaturalization method, there is a method of denaturalizing hemoglobin with a thiocyanate compound (refer to Patent Document 2). To be specific, this method is an analysis method for measuring a relative amount of a specific hemoglobin derivative in a blood sample, and comprises (a) a process of obtaining a denaturalized blood sample by processing a blood sample with (i) thiocyanate salt that can denaturalize substantially all hemoglobin existing in the blood sample, and has a concentration of 0.5˜0.6M in the sample, and (ii) an oxidizing agent that can transform substantially all hemoglobin existing in the blood sample to a form of methemoglobin, (b) a process of quantifying the methemoglobin in the denaturalized blood sample, (c) a process of quantifying a specific hemoglobin derivative in a denaturalized form in the denaturalized blood sample by immunoassay, and (d) a process of associating the test results obtained from the processes (b) and (c).
Furthermore, as still another denaturalization method, there is a method of denaturalizing hemoglobin with an ionic surface-activating agent (refer to Patent Document 3). To be specific, this method is a method for measuring a content of a hemoglobin derivative in a blood sample, and comprises (a) processing a blood sample with a hemolysis reagent including an ionic abluent having a pH of 5˜9.5, at a temperature of 4˜37° C. for up to ten minutes, and (b) immunologically measuring a hemoglobin derivative in the blood sample in which the hemoglobin derivative is hemolyzed.
Patent Document 1: Japanese Published Patent Application No. Hei. 3-51759
Patent Document 2: Japanese Published Patent Application No. Hei. 1-155268
Patent Document 3: Japanese Published Patent Application No. Hei. 6-11510